Helminth, protozoan and viral infections of the European eel, Anguilla anguilla

The European eel, Anguilla anguilla, is an important catadromous fish that has beenclassified as critically endangered due to severe population decline. The reasons for this arenot fully understood; however, infectious disease undoubtedly makes a contribution. To explorethis further, a total of 509 A. anguilla were sampled between 2008 and 2010 from 27 locationsacross England and Wales. Following dissection, the swimbladder nematode Anguillicoloidescrassus was found present in 245 specimens sampled from 20 locations (48.1%). Significantcorrelation was found between eel length and intensity of infection. However, no significantcorrelation between eel condition factor and A. crassus infection was found. To explore the A.crassus population further, microsatellite analysis of 7 loci from 72 nematodes, sampled from 10different locations, was conducted. Although multiple alleles (between 12 and 38) existed at allanalysed loci, genetic differentiation of A. crassus was low (average FST = 0.037). Furtheranalyses (STRUCTURE, BAPS and UPGMA phylogeny) showed the existence of two distinct A.crassus populations; one originating from the river Piddle and the other represented by theremaining sites.To examine eel for infection with the protozoan haemoflagellate Trypanosomagranulosum, a nested PCR assay was developed to amplify a region of the parasite 18S rRNAgene from heart tissue. Giemsa staining of eel blood sampled from specimens obtained theriver Gowy confirmed the robustness of the molecular diagnostic test. Overall, T. granulosumwas found to be highly prevalent (87.2%) in UK eel.A PCR-based assay for detection of the Herpesvirus anguillae (HVA) DMA polymerasegene was also developed. Heart screening revealed that H. anguillae was present in 176 eelsampled from 26 locations (34.5%). Tissue-based screening of river Gowy eel showed thatHVA detection was tissue dependent. Morphological examinations showed that some eelpresented clinical signs of HVA infection, though most did not, suggesting that the virus isprimarily latent.Overall, the prevalence of triple co-infections (A. crassus, T. granulosum and H.anguillae), varied significantly according to sampling location; however, there was noassociation between these infectious agents.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2012

Author dc:creator

• Ab Aziz, R

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1337761

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1337761